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52mm TB on VVC


jackb_ms

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I'm sure a lot of you have the 52mm TB of the MGF fitted on thier engines

 

Well, i had it as well! And I reverted to the 48mm!

When i was running the 52mm, i had a lot of hesitation, didn't notice any hike in performance but did notice in a hike in the petrol comsumption which isn't cool.

 

I wonder if i am the only one who did experienced this problem.

My car is a 21 and the engine was fitted in 1996

 

Jack

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I have the 52mm TB, revised Exhaust cam, fully flowed head (the car that is!) all done by DVA and It goes like stink, This conversion In an Elise gave 179bhp on Dave Walkers RR, with no changes to the ECU

 

You could try reseting the ECU, which may be the problem, also make sure you have taken off the excess plastic off the TB as it could rub on the body work.

 

My car has some other mods as well, VHPD exhaust, & forged pistons, I am waiting for Emerald to sort the VVC ECU, but only to see what the difference is and also to try DTH TB's which ought to be a first on a VVC!

 

Don't give up on the VVC yet

 

Mark Bennett

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I went from 48 to 52 on my 1.4K. Never had any hesitation problems with it.

 

Didn't notice any performance increase but had noticably smoother throttle response. My old plastic body housed 48mm was a bit sticky. If I could have got hold of a ali 48mm body I would have been just as happy.

 

 

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Poing.

 

Yep, I have a VVC with 52. I'm very happy with it now, and the rolling road turned up 173bhp FWIW. The reason for the dyno run was to tweak the Weber adjustable FPR that Ammo recommended to increase the fueling in light of the Piper exhaust cam, ported head and 52mm TB. The session went well, the operator (Ray @ T&M in Colchester, incredibly knowledgable guy) tweaked it up to around 3.4 bar, curing some lean running and liberating about 5bhp minimum across the rev range.

 

It doesn't hesitate any more than it did with the 48mm TB, I'd venture that your TB issue is a symptom rather than a cause.

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This has come up a few times recently. Worth clarifying that the MEMS is not a *learning* ECU. It might learn a thing or two about where to set the IACV to control idle, but it doesn't learn anything else.

 

This means that if you change one of the fundamentals in the system (TB, injectors, fuel pressure) then it will fall out of calibration and won't run the engine very well. It does however work quite well with cam changes as long as you keep the TB the same.

 

How is this possible?

 

Well the MEMS determines airflow by looking at the MANIFOLD ABSOLUTE PRESSURE achieved by flowing air from atmospheric pressure past a known restriction (a known TB open to a measured angle). Simple really.

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Thank very much for your answer

 

The way i would like to go it's to have a fully mapable ECU but it is not ready...Yet *smile*

 

Luke

 

I will have my head done and have the exhaust cam fitted by DVA power latter on this year.

I would be very interested in which Weber adjustable FPR you are using.

 

Jack

 

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Jack, it's a Weber WFR040. Nominal 3 bar regulator with 8mm hose tails for in & out. I made a little alu bracket to hang it off the foremost bolt that holds the plenum halves together, and lathed up a plug to blank off the hole in the fuel rail when you take the stock one out.

 

The Piper reprofile is a demon. Totally changes the character of the engine, which was a little too leisurely for my liking. Now it sort of 'comes on cam' at about 4k5 and just screams to the redline big style.

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Hi Luke

 

I've emailed Darryl Richards and this is his answer:

I am not familiar with the actual item you requested? "Weber WFR040"

However I have a fuel regulator suitable for Webers and most normally aspirated carburettor cars. It's adjustable from 0-5p.s.i. comes with a s/steel fixing bracket.

 

Now i'm a bit confused 🤔

Do you remember who you spoke 2?

Can you e-mail some pic, of ur installation

 

Cheers

 

Jack

 


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Please explain what the differance is?

 

as I understand it the FSE valve has a higher rate spring so the fuel pressure increases more rapidly with rpm. the adjustment is on the initial pressure datum but not the rate

 

the webber one again alows you to adjust the pressure datum (i.e pressure at idle) but the rate of increase is the same as a standard regulator?

 

is that correct or have I got this completely wrong

 

Simon

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The one quoted by Jack's friend is for carbs. That was what oily was pointing out.

 

Any adjustable FPR will do. The power boost aspect of the FSE valve is a characteristic which may be good or bad. Worth remembering that this is a bodge correcting fuelling parameters when some other part of the system has been taken outside its design spec. Results should be judged on their delivery of results, so if others have had success with the FSE valve you can do the same.

 

It is important to understand that the engine is no longer "mapped"; it is just close enough to do a decent job after these combined mods.

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I was present at Luke's rolling road tune and the results with the Weber FPR were very good. Fuelling was pretty much spot on thanks Ray's skill and experience.

 

Once the fuel pressure was up enough to be correct at the top end, the bottom end went too rich. Connecting the vacuum pipe to to the inlet manifold corrected this (just). I don't usually use the vaccuum pipe on these regulators as we usually have the facility to map the ECU.

 

The fuel pressure regulator trick is not as good as a new ECU and a re-map, but in this case is so close that it doesn't warrant having anything else done to it (it was better than any car on carbs). I would be happy to run my own car in this state. The regulator cost £60.00, a new ECU £600.00 ? Plus I don't think there is an ECU that can control the VVC.

 

Considering that the engine has a head that has been ported and skimmed, a new exhaust cam has been fitted, a larger throttle body and different exhaust there was a certain element of luck involved. Had it not worked then a rethink would have been in order.

 

I have been using the Weber regulators for over ten years and they have never let me down, so no need to change to another brand. I have never used FSE ones but have heard some stories from engine builders that make me a bit wary of them. There are probably a few people who contribute to this forum who use FSE FPRs who can comment based on personal experience.

 

The important thing is that Luke had a really stupid grin on his face after he drove the car. 😬

 

AMMO

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More of an educated grin, I think you'll find *cool*

 

Dunno, Jack. My local branch of Bennetts gave me the number of Weber tech support. I phoned them and explained my needs. The guy faxed me the FPR page from their catalogue, I worked out which I needed and gave the WFR040 number to Bennetts, who managed to order me one overnight. WFR040 is the number that's listed in the "Part number" column of the catalogue.

 

FWIW I spoke to Andy Gray in Weber technical.

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I don't understand, I have just purchased a Webber WFR040 and it is not adjustable, what am I doing wrong?

 

there is cap in the top which is where I wouls expect an adjuster to be but it would take some serious effort to get it out

 

is there two types of WFR040? or was the adjustment more brutal, i.e lever the cap out.

 

I am off for a RR session at lunchtime and was hoping to be able to adjust this but not really sure what to do now

 

any advice appreciated

 

or any one have Ammo's phone no so I can chat

Simon

 

07976 633997

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AMMO, no need to be sorry, I was just confused as it did not look as though the cap would come off, and I did not want to try too hard as I thought I might do damage and I thought I might be sending the unit back

 

Thanks

 

Simon

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Jack,

 

I got it from Hoopers of bristol, 0117 9676563, they had to order it but got thier supplier to send it direct to me so it took 2 days, about £62 including postage.

 

The tamper proof cap really had me confused it was so well located I had to drill it off!!

 

You wil need to machine up a blank for the origional reg fitted in the fuel rail

 

Simon

 

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